In recent years, a typical liquid crystal display device includes a backlight and a liquid crystal panel, the liquid crystal panel including two polarizers and a liquid crystal layer sandwiched between the two polarizers. A typical liquid crystal display device displays an image by controlling the alignment of liquid crystal molecules by means of voltage. The backlight emits light, which enters the liquid crystal panel in an unpolarized state. Thus, half of the light is absorbed by the polarizer through which the light first passes.
Patent Literature 1 discloses a technique for reducing a light loss caused by a polarizer. The technique of Patent Literature 1 provides a polarized-light selection reflecting surface on a light entry side of a prism array, and also provides a ¼ wavelength plate and a reflecting mirror on a side toward which light reflected by the polarized-light selection reflecting surface travels. The light source emits light toward the polarized-light selection reflecting surface, the light including polarized light that is incapable of passing through the polarized-light selection reflecting surface. Such polarized light is reflected by the polarized-light selection reflecting surface to subsequently strike the ¼ wavelength plate and the reflecting mirror, which are provided ahead of the reflected light. For improved efficiency for light utilization, the polarized light reflected by the polarized-light selection reflecting surface needs to be changed into polarized light that is capable of passing through the polarized-light selection reflecting surface and to be then emitted to the polarized-light selection reflecting surface again. To achieve such an arrangement, the technique of Patent Literature 1 disposes the ¼ wavelength plate and the reflecting mirror at such positions that the ¼ wavelength plate and the reflecting mirror are located apart from the prism array and the polarized-light selection reflecting surface provided on the side toward which light reflected by the polarized-light selection reflecting surface travels. With this arrangement, (i) P polarized light, for example, included in the light emitted by the light source passes through the polarized-light selection reflecting surface, whereas S polarized light included in the light is reflected by the polarized-light selection reflecting surface, (ii) the S polarized light reflected by the polarized-light selection reflecting surface passes through the ¼ wavelength plate and is then reflected by the reflecting mirror to become P polarized light to be emitted again to the polarized-light selection reflecting surface, and (iii) the P polarized light thus emitted passes through the polarized-light selection reflecting surface. The above arrangement consequently allows reuse of reflected polarized light.